1. Field of the Invention
The present relates generally to fuel tanks for motor vehicles, and more particularly to plastic powder, rotational molded tanks having a recessed filler neck for positioning the cap flush with the exterior surface of the fuel tank.
2. Background Art
Receptacles for containment of flammable fuels, particularly in regard to motor vehicles such as boats, automobiles or aircraft, require substantial integrity to avoid leakage and from seams, fittings and wall areas, particularly during deformation of fuel tanks upon impact of a motor vehicle. Resilient materials such as plastics have been used to replace the traditional metal fuel tank structures where the integrity of the walls and the seams that join the walls was at risk. These materials have been advantageously employed in tanks supplied for racing vehicles where the opportunity for high speed impacts is enhanced. However, fill closures or valves for the tanks have not previously been implemented with the materials used to form the tanks. In particular, economy valves, fast fill valves and regular fill fittings are generally mounted onto the top surface of the fuel tank, generally in a manner protruding above the top exterior surface of the tank.
Typically, the previously known tank structures are completed by installing a separately fabricated fuel inlet attachment. Some of these inlets include a neck portion recessed below the top surface of the tank at an edge of an opening in the top tank surface formed to receive the inlet or valve. However, such necks depend from an annular flange which must be retained by bolting or the like to the tank wall surrounding the peripheral edge of the opening. Accordingly, the mounting structure of these previously known recessed necks still include protrusions such as bolts, nuts, flanges and any handles on the caps, even though a large portion of the cap is received within the recessed neck. These protrusions form an obstruction during shifting movement of the tank or forced engagement with other motor vehicle parts which may come in contact with the tank during uncontrolled vehicle movement.
Moreover, the separate mounting of a fill neck or valve onto the fuel tank walls forms a seam or interface which is subject to leakage even under normal usage. In particular, the use of bolts to secure a mounting flange to the top surface of the plastic tank imposes inconsistent pressures to the flange and the supporting wall portion of the fuel tank as well as any seals interposed between mating surfaces around the entire periphery of the valve opening. As a result, under particularly stressed or strained conditions, the uneven application of pressure around the opening may contribute to leakage between the part as well as actual rupturing of the parts of the connection between the attached or adjacent parts.